RNA-INTERFERENCE
Every gene in a normally operating cell performs its own strictly defined function. For example, it can be responsible for protein production, or mRNA, or for interaction with other regulatory proteins. In this case they speak of a normal expression of this gene in the cell (from the Lat. expressus - expressive, explicit). However, if the amount of the product of a certain gene (for example, some protein) decreases, then they speak of decrease of this gene expression. The effect of "suppression" of the expression of certain genes by small RNAs is called RNA-interference. The RNA-interference process is used by eukaryotes for pre- and post-transcriptional modulation of gene expression. This mechanism helps the immune system of an organism to preserve integrity of the genome. For example, the apparatus of RNA-interference is necessary for lower eukaryotes and plants for silencing of transposones, resistance to viruses, and preserving stability of chromosomes.